Sunday, February 15, 2015

node-red update, new rpi-gpio node is great

A few days ago a new version of node-red was released: 0.10.1, details on the node-red blog. Tons of new features are in this release as detailed in the article I just mentioned but for me one stands out: the new rpi-gpio node.

A couple months ago I tried to use a PIR sensor with node-red on my Raspberry Pi but using interrupts didn't work as expected, as I mentioned here. The new rpi-gpio node was completely rewritten by Dave C-J as detailed in this thread in the node-red Google group. As mentioned here and also in the node-red release notes, the new node uses the built in RPi.GPIO python library (part of of the newer Raspbian distributions) instead of the wiringpi library; to make sure you have the necessary files do:

sudo apt-get update
sudo apt-get install python-dev python-rpi.gpio
~/node-red/nodes/core/hardware/nrgpio ver 0

Last command should reply 0.5.8 (or better) which is the version of the RPi.GPIO library.

I installed the new node-red version and followed the steps mentioned above (even if I may not have had to since I am using the latest Raspbian, released last year in December) and the last command returned 0.5.9. I connected the PIR sensor to the Pi as mentioned in this ModMyPi article: VCC to +5V [Pin 2], GND to GND [Pin 6] and OUT to GPIO 7 [Pin 26]. Added a new rpi-gpio in node to the editor, configured it to use pin 26, deployed and it worked from the first try. Simply awesome! Even more awesome: in the new node-red version the node status option is on by default so I didn't even need to add a debug node: I can see the rpi-gpio node's status reporting 1 as soon as something moves in front of the PIR sensor and 0 when it resets.

One great thing about the PIR sensor I am not sure I ever mentioned is this: even when the motion sensor is powered with 5V, the output voltage on the data pi is 3.3V (high) and 0V (low); I found this info in several places, in the ModMyPi article mentioned above, on the Learn Adafruit website and a couple more places like this instructable. This makes it perfect to be used with Raspberry Pi without any worries about the voltage applied on the data pin.

To end this short post, there is something I wanted to mention for a while: even if I keep finding new frameworks and services out there (for example, a couple days ago I discovered Lelylan and OpenHAB is on my list of things to study deeper), node-red is the service I keep coming back to every time I need to write an app on my Pi, GPIO related or not: it may not have the fancy charts other services have and it may not have the rule engine others do, but nothing beats node-red when you need to come up with real functionality fast, to connect services easily without having to write new code from scratch each time. I really love it! Give it a try - you will love it, too.

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